Minimally invasive posterior cervical facet arthrodesis shim implant and tools therefor
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Publication Number
US-11583408-B2
Publication Date
2023-02-21
Expiration Date
Abstract
The shim-type implant for distraction and fusion of cervical facet joints is provided. The implant has a generally box-like shape with a blunt leading edge that may be centered or offset to the inferior face. The implant may include a graft window for enhanced osseous through-growth after implantation. The implant is coated with hydroxyapatite (HA) and/or tri-calcium phosphate (TCP) to allow for osteo-conduction, is porous, and has a roughened surface with serrations on the superior and inferior faces. The implant may be fabricated from a titanium or tantalum alloy. In an embodiment, a set of tools is provided with a chisel and one or tongs and one or more decorticators for inserting the implant.
Core Innovation
The invention describes a minimally invasive posterior cervical facet arthrodesis shim implant and a coordinated nested tool system for fusion of a cervical facet joint from a posterior approach. The shim implant includes a generally rounded or box-shaped body with a distal face, a proximal face, superior and inferior surfaces, and two side faces. The implant distal face has a rounded profile defined by an arc, and the proximal face includes one or more insertion device engagement features.
The implant is fabricated from titanium metal or alloy or tantalum metal or alloy and has a roughened surface. The implant is coated with hydroxyapatite or tri-calcium phosphate or both and is porous to allow for bone in-growth. The superior and inferior surfaces each include serrations with a plurality of grooves spanning the transverse axis, and optional graft-window perforations through the implant thickness are described.
A set of tools is provided for preparing the facet joint and implant placement, coordinated to align and nest. An entry chisel includes two cannulation channels running the length of the chisel shaft for accepting guidewires, and the chisel shaft has rounded superior and inferior surfaces and flattened sides for rotational stability. A tong system is described in which the chisel is inserted into a channel in a tong to a nested position, with alignment maintained between the chisel distal tip and tong prongs, followed by decortication and rasping to facilitate fusion and gauge the height of the final implant.
Claims Coverage
The relevant portion contains one independent claim with multiple dependent claims. The independent claim includes inventive features covering the shim implant structure and a coordinated nested tool set comprising an entry chisel, tongs, a decorticator, a rasp, and a threaded inserter.
Porous coated shim implant with serrations and grooves
A generally rounded or box-shaped shim implant for fusion of a cervical facet joint from a posterior approach, having a roughened surface, coated with hydroxyapatite or tri-calcium phosphate or both, and porous to allow for bone in-growth, wherein the superior and inferior surfaces each comprise serrations with a plurality of grooves spanning the transverse axis.
Entry chisel with dual guidewire cannulations and rotational stability
An entry chisel for the posterior approach, having a distal end with smooth inferior and superior surfaces and a uniform cross-sectional profile, wherein the chisel shaft has rounded superior and inferior surfaces and flattened sides, and wherein the chisel shaft has two cannulation channels running the entire length thereof, each adopted for accepting a guidewire.
Nested chisel-in-tong alignment using a channel-matched tong
A tong system with a first tong having two prongs at a distal end and a channel along the entire length of the first tong, wherein the interior cross-section of the channel matches the uniform cross-sectional profile of the chisel so that the chisel can be inserted in the channel from a proximal end to a nested position, and wherein rounded superior and inferior surfaces and flattened sides of the chisel maintain rotational stability and the distal tip is aligned with the prongs.
Posterior decortication and gauging using aligned decorticator and rasp in the tong
A coordinated procedure in which the chisel nested in the first tong is inserted into a channel in a proximal end of a first decorticator for decorticating a facet joint between two vertebrae from a posterior approach using a jagged distal end with teeth, after which the decorticator is withdrawn and a rasp is inserted into the channel in the first tong and manipulated to remove tissue to facilitate fusion and gauge the height of the final implant.
Threaded inserter that secures the shim implant and disconnects to leave it in position
Placement and securing of a shim implant in the facet joint using an inserter with a shaft, an axle within the shaft, a handle that turns the axle, and a male-threaded connection at a distal end of the axle screwed into a female-threaded engagement feature on the implant, with at least one prong aligned with another engagement feature on the proximal face of the implant; the inserter is inserted into the channel in the first tong, the handle is turned to disconnect the implant from the inserter, and the first tong is withdrawn leaving the implant securely in position.
Across the independent and dependent claims shown, the core coverage centers on a posterior-approach cervical facet fusion shim implant with a coated porous roughened body and surface serrations, and a coordinated nested tool set that aligns an entry chisel, tongs, a decorticator, and a tong-channel rasp before securing the implant using a threaded inserter that is disconnected while leaving the implant in position.
Stated Advantages
Improves radiologic contrast.
Provides osteoconduction and through-growth via a porous structure coated with hydroxyapatite or tri-calcium phosphate or both.
Reduces tissue damage during posterior MIS implantation.
Documented Applications
Fusion of a cervical facet joint from a posterior approach using a minimally invasive posterior surgery shim implant and coordinated nested tool system.
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